Statistics
| Branch: | Revision:

ffmpeg / libavutil / random_seed.c @ b65c1ccf

History | View | Annotate | Download (2.12 KB)

1
/*
2
 * Copyright (c) 2009 Baptiste Coudurier <baptiste.coudurier@gmail.com>
3
 *
4
 * This file is part of FFmpeg.
5
 *
6
 * FFmpeg is free software; you can redistribute it and/or
7
 * modify it under the terms of the GNU Lesser General Public
8
 * License as published by the Free Software Foundation; either
9
 * version 2.1 of the License, or (at your option) any later version.
10
 *
11
 * FFmpeg is distributed in the hope that it will be useful,
12
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14
 * Lesser General Public License for more details.
15
 *
16
 * You should have received a copy of the GNU Lesser General Public
17
 * License along with FFmpeg; if not, write to the Free Software
18
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19
 */
20

    
21
#include <unistd.h>
22
#include <fcntl.h>
23
#include "timer.h"
24
#include "time.h"
25
#include "random_seed.h"
26
#include "avutil.h"
27

    
28
static int read_random(uint32_t *dst, const char *file)
29
{
30
    int fd = open(file, O_RDONLY);
31
    int err = -1;
32

    
33
    if (fd == -1)
34
        return -1;
35
    err = read(fd, dst, sizeof(*dst));
36
    close(fd);
37

    
38
    return err;
39
}
40

    
41
static uint32_t get_generic_seed(void)
42
{
43
    int last_t=0;
44
    int bits=0;
45
    uint64_t random=0;
46
    unsigned i;
47
    int s=0;
48

    
49
    for(i=0;bits<64;i++){
50
        int t= clock()>>s;
51
        if(last_t && t != last_t){
52
            if(i<10000 && s<24){
53
                s++;
54
                i=t=0;
55
            }else{
56
                random= 2*random + (i&1);
57
                bits++;
58
            }
59
        }
60
        last_t= t;
61
    }
62
#ifdef AV_READ_TIME
63
    random ^= AV_READ_TIME();
64
#else
65
    random ^= clock();
66
#endif
67

    
68
    random += random>>32;
69

    
70
    return random;
71
}
72

    
73
uint32_t av_get_random_seed(void)
74
{
75
    uint32_t seed;
76

    
77
    if (read_random(&seed, "/dev/urandom") == sizeof(seed))
78
        return seed;
79
    if (read_random(&seed, "/dev/random")  == sizeof(seed))
80
        return seed;
81
    return get_generic_seed();
82
}
83

    
84
#if LIBAVUTIL_VERSION_MAJOR < 51
85
attribute_deprecated uint32_t ff_random_get_seed(void);
86
uint32_t ff_random_get_seed(void)
87
{
88
    return av_get_random_seed();
89
}
90
#endif